Since solar ultraviolet (UV) light is the major cause of skin cancer, it is important to identify the UV induced cellular lesions which may contribute to the carcinogenic process. In addition to pursuing the role of DNA damage, the importance of UV induced alterations of other cellular components must also be considered. It is the aim of the current study to investigate disruption of the cytoskeleton resulting from exposure of cultured cells to environmentally relevant wavelengths of UV light. The cytoskeleton has been selected for investigation since it is an important participant in the regulation of normal cell growth, and disruption of this complex cytoplasmic structure may result in detrimental cellular dysfunctions. Normal human skin fibroblast and epidermal keratinocyte cell strains, cultured under varying growth conditions, will be utilized to characterize UV light induced alterations of cytosketetal microtubules, microfilaments and intermediate filaments. Cytoskeletons of cells exposed to polychromatic UV light composed of environmentally relevant wavelengths or to the more commonly used short wavelength (254 nm) UV light will be studied by fluorescence microscopy. The cytoskeleton of keratinocytes which have been UV irradiated at different stages of differentiation will also be examined. In addition, the cytoskeleton of fibroblasts derived from patients with xeroderma pigmentosum, Bloom's syndrome and Cockayne's syndrome will be investigated in order to determine if cytoskeletal damage may contribute to the photosensitivity of cells. Having determined that long wavelength UV light disrupts microtubules in normal cells, experiments will be performed to differentiate between the disruption of microtubules resulting from damage to microtubules assembled prior to irradiation or from changes in unassembled dimeric tubulin subunits. This will be accomplished by examining the effect of UV light on extracted cytoskeletons and by studying the repolymerization of tubulin in cells which contain only the dimeric form of tubulin at the time of irradiation. The role of reactive oxygen species in the formation of altered cytoskeletons will also be explored. Furthermore, tubulin extracted from UV irradiated and control cells will be examined using SDS polyacrylamide gel electrophoresis in order to determine if UV light induces the formation of high molecular weight, cross-linked tubulin.